Probe device and probe method

ABSTRACT

A probe device  20  having a contact load monitoring device  10 . This contact load monitoring device measures the displacement of a loading table caused by a contact load exerted on the mounting table from a probe in an overdrive by means of a displacement sensor  11  disposed in the space below the mounting table as a sinkage quantity. This sinkage quantity is collated with a correlation table to determine the contact load. If the contact load is less than the designed contact load, the mounting table is further overdriven.

The present application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Application No. 2001-367266 filed on Nov.30, 2001, the entire contents of which are incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to a probe device; and, more particularly,to a probe device capable of detecting a contact load, which is exertedon a mounting table when probes are in contact therewith duringinspection, based on an amount of resultant sinking of the mountingtable.

BACKGROUND OF THE INVENTION

In an inspection process of a semiconductor device, a probe device iswidely employed as an inspection device of a semiconductor wafer(hereinafter referred to as a wafer) As shown in FIGS. 2A and 2B, theprobe device includes a loader chamber 1 and a prober chamber 2, andinspects electrical characteristics of semiconductor devices(hereinafter referred to as “devices”) formed on the wafer. Incorporatedin the loader chamber 1 are a cassette mounter 3 for mounting thereon acassette C accommodating therein a plurality (e.g., 25 sheets) of wafersW; a wafer transfer mechanism 4 for transferring wafers W from thecassette mounter 3 sheet by sheet; and a pre-alignment mechanism(hereinafter referred to as a “sub-chuck”) 5 for pre-aligning the wafersW transferred via the wafer transfer mechanism 4. The prober chamber 2includes a mounting table 6 (hereinafter referred to as a “main chuck”)which is moved in X, Y, Z and θ directions via an XY-table, a lineardriving mechanism and a θ driving mechanism; an alignment mechanism 7which performs alignment of a wafer W in cooperation with the main chuck6; a probe card 8 disposed above the main chuck and provided with anumber of probes 8A; and a test head T interposed between the probe card8 and a tester (not shown). The probe device further includes a displayunit 9 for displaying, e.g., an operational menu and an inspectionresult.

In the prober chamber 2, after the wafer W is aligned with the probes8A, the main chuck 6, on which the wafer W is mounted, is index fedwhile concurrently being elevated, so that the probes 8A are broughtinto contact with electrodes on the devices formed on the wafer W at apredetermined probe pressure (contact load). The electricalcharacteristics of the devices are inspected while such a contact stateis being maintained. At this time, by overdriving the main chuck 6relative to the probes 8A by a predetermined amount, the probes 8A areconsidered to be in electrical contact with the wafer W under asubstantially constant contact load.

Recently, however, the number of devices that need to be measuredsimultaneously (the number of simultaneous measurements) is increasing.For example, the number of simultaneous measurements is as many as 32and the contact load between the probes 8A and the main chuck 6 isgreater than 20 kg. Moreover, the probe card 8 is repeatedly expandedand contracted due to an aging thereof of the probe card 8 or a thermalinfluence from an accelerated test conducted at a high temperature. As aresult, the contact load of the probe card 8 that acts on the main chuck6 varies despite a constant amount of overdriving of the main chuck 6.Therefore, there is a need for a stabilization of the contact load.

For example, FIG. 3 schematically describes such a phenomenon. The mainchuck 6 does not rise up to a target position during an overdrive stage,which is marked by a dashed dotted line in FIG. 3, but instead sinks toa position marked by a solid line in the same drawing due to the contactload exerted on the main chuck 6 by the probe card 8. That is, the mainchuck 6 is lowered by a slight amount of distance δ, resulting in afailure to obtain a desired contact load. Consequently, an inspectionreliability is reduced. Conversely, if an overdriving amount isdetermined by predicting an amount of sinking of the main chuck 6, thecontact load may become excessively large, to shorten a lifetime of theprobe card 8.

The applicant proposed a probe method and a probe device employing apressure sensor in Japanese Patent Publication Laid-open No.2001-110857. In case of measuring a load by using the pressure sensor,the pressure sensor detects a pressure based on a deformation of itself.Since the pressure sensor is placed near an operating point of the load,e.g., directly underneath the mounting table, i.e., between the mountingtable and the linear driving mechanism, the deformation of the pressuresensor itself increases a displacement of the mounting table. Thus, acertain amount of time is required to correct the load including the isdeformation of the pressure sensor itself.

Furthermore, the applicant proposed in U.S. patent application Ser. No.09/776,686 that a measurement mechanism provided with a linear sensorand a linear scale be installed at a peripheral portion of a supportmember of the main chuck in order to measure a contact load between themain chuck and the probes. Since, however, the measurement mechanism isdisposed at the peripheral portion of the support member of the mainchuck, additional space around the peripheral portion of the supportmember needs to be allocated therefor. Further, there may be produced anerror resulting from expansions and contractions of the linear scale dueto a temperature change.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to solve theabove-mentioned problems. In accordance with one aspect of the presentinvention, a constant contact load can be obtained by detecting acontact load through a sinking amount of a mounting table (hereinafterreferred to as a main chuck) during inspection. In accordance withanother aspect of the present invention, a highly reliable inspectioncan be performed. In accordance with still another aspect of the presentinvention, there is provided a probe device capable of rapidly revisinga load without deforming a sensor. In accordance with still anotheraspect of the present invention, a displacement sensor for measuring thesinking amount of the mounting table can be located in an efficientspace. In accordance with still another aspect of the present invention,the sinking amount of the mounting table can be accurately obtained.

Other objects and advantages of the present invention will be describedin a specification to be provided hereinafter, and some of them willbecome apparent from a corresponding description or from animplementation of the present invention. Corresponding objects andadvantages of the present invention are accomplished and obtained bymeans particularly specified herein and a combination thereof.

In accordance with one aspect of the present invention, there isprovided a probe device for inspecting electrical characteristics of anobject W to be inspected, including: a mounting table for mountingthereon the object to be inspected, the mounting table being movable inX, Y, Z and θ directions; a probe card disposed above the mounting tableand provided with a plurality of probes; and a contact load monitoringdevice including at least one displacement sensor and a control deviceand monitoring a contact load exerted on the mounting table by theprobes during an overdriving stage, wherein the displacement sensor isdisposed in a space below the mounting table and measures, as an amountof sinking, a displacement of a reference surface at a bottom side ofthe mounting table caused by the contact load exerted on the mountingtable by the probes during the overdriving stage; wherein the controldevice is provided with a correlation table for amounts of sinking ofthe reference surface of the mounting table and contact loads andestimates a contact load by using the displacement measured by thedisplacement sensor and the correlation table; and wherein the controldevice adjusts the contact load to be identical with a designed contactload by further elevating the mounting table in case the contact load isless than the predetermined designed contact load.

Preferably, the displacement sensor of the probe device may bepreferably an analog output or a digital output displacement sensor.

Further, the displacement sensor of the probe device may be preferably acapacitive displacement sensor or an eddy current displacement sensor.

Moreover, it may be preferable that the displacement sensor is disposedat at least one of a center of the mounting table and plural locationstherearound.

In accordance with another aspect of the present invention, there isprovided a method for inspecting electrical characteristics of an objectto be inspected by using the probe device of claim 1, including thesteps of: (a) setting a designed overdriving amount and a designedcontact load corresponding to the object W to be inspected in thecontrol device; (b) bringing the object to be inspected into contactwith the probes by elevating the mounting table on which the object tobe inspected is mounted; (c) overdriving the mounting table based on thedesigned overdriving amount; (d) monitoring whether the contact loadexerted on the mounting table is identical with the designed contactload by using the contact load monitoring device, wherein the monitoringstep (d) has the steps of: (d1) measuring the displacement of thereference surface at a bottom side of a support member as the amount ofsinking of the mounting table and outputting the measured displacementto the control device by the displacement sensor; (d2) estimating thecontact load corresponding to the displacement based on the correlationtable and comparing the estimated contact load with the designed contactload by the control device; (d3) further elevating the main chuck incase the contact load estimated based on the displacement measured bythe displacement sensor is less than the designed contact load; and (d4)repeating the steps (d1) through (d3) and stopping the elevation of themain chuck when the contact load based on the displacement measured bythe displacement sensor reaches the designed contact load and (e)inspecting the electrical characteristics of the object W to beinspected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross sectional view of main parts of a probedevice in accordance with a first preferred embodiment of the presentinvention;

FIGS. 2A and 2B describe an example of a conventional probe device,wherein FIG. 2A is a partial cutaway view showing main parts thereof andFIG. 2B is a plan view thereof;

FIG. 3 illustrates an electrical contact state between a probe of theprobe device and a wafer shown in FIGS. 2A and 2B;

FIG. 4 provides a schematic cross sectional view of main parts of aprobe device in accordance with a second preferred embodiment of thepreset invention; and

FIGS. 5A and 5B set forth a flow chart schematically explaining a probemethod in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described with reference to anembodiment shown in FIG. 1. As shown in FIG. 1, a probe device 20 of thepresent embodiment is provided with a contact load monitoring device 10for monitoring a contact load exerted by a probe card 22 duringinspection.

The probe device 20 of the preferred embodiment will now be described.As shown in FIG. 1, the probe device 20 of the present invention mayinclude, for example, an XY stage 26; a linear driving mechanism 27; amain chuck 21 capable of moving in X, Y, Z and θ directions whilecarrying a wafer W mounted thereon; the probe card 22 disposed above themain chuck 21 and provided with a plurality of probes 22A; and analignment mechanism 7 (see FIG. 2A) to determine the position of thewafer W mounted on the main chuck 21. Under the control of a controldevice 23, the aligned main chuck 21 is elevated, so that the wafer W isbrought into contact with the probes 22A. Electrical characteristics ofdevices formed on the wafer W are inspected while such a contact stateis maintained.

The main chuck 21 is mounted on the XY stage 26. The XY stage moves in Xand Y directions. Provided on the XY stage is the linear drivingmechanism 27 formed of, e.g., a ball screw 27A. The linear drivingmechanism 27 moves the main chuck 21 up and down in a vertical direction(Z direction) and is embedded in, e.g., a support member 21A forsupporting the main chuck 21. The support member 21A is elevatablyaccommodated in a housing 25 via bearings 24. The main chuck 21 is movedup and down in the vertical direction (Z direction) via the lineardriving mechanism 27 in the housing 25.

The contact load monitoring device 10 includes a displacement sensor 11positioned in a space below the mounting table. As shown in FIG. 1, thedisplacement sensor 11 measures a displacement of a reference surface21B at a bottom side of the support member 21 as the amount of sinkingof the main chuck 21. The contact load monitoring device 10 monitors theamount of sinking of the main chuck 21 caused by a contact load exertedon the main chuck during inspection. A conventional analog or digitaloutput displacement sensor, for example, can be employed as thedisplacement sensor 11. The analog output sensor may be, e.g., acapacitive displacement sensor, an eddy current displacement sensor orthe like. The digital output displacement sensor may be, e.g., a laserinterference displacement sensor. Further, the displacement sensor 11 isnot limited to such a non-contact sensor but instead can be of a contactsensor.

In the preferred embodiment, the displacement sensor 11 can be disposeddirectly underneath the support member 21A, as shown in FIG. 1. Thebottom end surface 21B of the support member 21A can be used as thereference surface 21B of the bottom side of the main chuck 21.Therefore, if the contact load is exerted on the main chuck 21, thedisplacement sensor 11 can detect the amount of sinking of the mainchuck 21 through the support member 21A.

Thus, various loads are subsequently applied to plural spots on the mainchuck 21 in advance, and a load applied to each spot and itscorresponding amount of sinking are measured. Such measurement can becarried out by measuring a change in the distance between the bottom endsurface 21B of the support member 21A and a bottom surface 25A of thehousing 25. Further, a correlation between a contact load and adisplacement provided by the displacement sensor 11 is obtained at eachof the plural spots on which the loads are applied, and a correlationtable created based thereon is stored in a memory unit of the controldevice 23. By collating the displacement obtained by the displacementsensor 11 with data in the correlation table, the contact load isobtained, which is then fedback to the linear driving mechanism. At thispoint, the contact load and so on may be displayed on the display unit 9(see FIG. 2). A designed overdriving amount for the wafer W to beinspected is also set in the control device 23 in advance. The designedoverdriving amount is used as a reference (target) of an overdrivingamount during inspection.

In inspecting the electrical characteristics of the wafer W, the mainchuck 21 is overdriven based on the designed overdriving amount. If theprobes 22A of the probe card 22 apply a contact load on the wafer Wmounted on the main chuck 21, the main chuck 21 sinks. The amount ofsinking is detected as a displacement by the displacement sensor 11. Thecontrol device 23 estimates a contact load corresponding to thedisplacement based on the correlation table, and compares the estimatedcontact load with a designed contact load. In case the estimated contactload is less than the designed contact load even after the main chuck 21is overdriven by a distance corresponding to the designed overdrivingamount, the control device 23 further overdrives the main chuck 21. If aresultant estimated contact load reaches the designed contact load, thecontrol device 23 stops the linear driving mechanism 27. In this state,the wafer W mounted on the main chuck 21 is inspected for the electricalcharacteristics thereof. Accordingly, the probe device 20 can alwaysperform an inspection of each device on the wafer W under apredetermined contact load (designed contact load).

Next, an operation of the probe device 20 employing the contact loadmonitoring device 10 will now be described.

(S1) A designed overdriving amount and a designed contact loadcorresponding to a wafer W are set in the control device 23 in advance.

(S2) Then, an inspection is initiated. The wafer W is mounted on themain chuck 21 by the wafer W transfer mechanism 4 (see FIG. 2B) in theloader chamber under the control of the control device 23.

(S3) The main chuck 21 is moved in the X, Y and θ directions based ondata from the alignment mechanism 7 (see FIG. 2A) to thereby align thewafer W to the probes 22A.

(S4) By moving the main chuck in the X, Y and θ directions,to-be-inspected devices, among devices formed on the wafer W, arelocated underneath the probes 22A.

(S5) The main chuck 21 is moved to a first inspection position. Devicesto be inspected first are located directly underneath the probes 22A bythe main chuck 21 and the main chuck 21 is elevated within the housing25 along with the support member 21A by the linear driving mechanismunder the control of the control device 23, so that the wafer W mountedon the main chuck 21 is brought into contact with the probes 22A of theprobe card 22.

(S6) Further, the linear driving mechanism overdrives the main chuck 21based on the designed overdriving amount until the main chuck 21 reachesa position (marked by a dashed dotted line in FIG. 1) at which thedesigned contact load is expected to be obtained. Since, however, a contact load is exerted on the main chuck 21 in a direction marked by anarrow in FIG. 1, the main chuck 21 sinks from a position marked by thedashed dotted line to a position marked by a solid line in FIG. 1.Consequently, the designed contact load cannot be attained even thoughthe main chuck 21 is elevated by a distance corresponding to thedesigned overdriving amount.

(S7) The contact load monitoring device 10 monitors whether the designedcontact load is obtained. That is, the main chuck 21 sink slightly owingto the contact load applied from the probe 22A to the main chuck 21overdriven by the control device 23. The displacement sensor 11 detectsthat amount of sinking as the displacement of the reference surface 21Bat the bottom side of the support member 21A. The displacement sensor 11then outputs the detected displacements to the control device 23.

(S8) The control device 23 estimates the contact load corresponding tothe detected displacement based on the correlation table.

(S9) Then, the estimated contact load is compared with the designedcontact load.

(S10) If the applied contact load is found to be less than the designedcontact load even after the main chuck 21 is elevated by as much as thedesigned overdriving amount to thereby be located at the position markedby the solid line in FIG. 1, the main chuck 21 is further raised up tothe position indicated by the dashed dotted line in FIG. 1 under thecontrol of the control device 23.

(S11) When a contact load estimated based on a displacement detected bythe displacement sensor 11 becomes identical with the designed contactload, the control device 23 outputs a stop signal to the linear drivingmechanism. Then, the elevation of the main chuck 21 is stopped by thelinear driving mechanism.

(S12) In this state, the electrical characteristics of the devicesformed on the wafer W mounted on the main chuck 21 are inspected.

(S13) It is checked whether all the to-be-inspected devices formed onthe wafer are inspected.

If any device to be inspected is not inspected, the step S4 is repeatedto inspect such devices.

If all the to-be-inspected devices are inspected, the linear drivingmechanism 27 lowers the main chuck 21.

In accordance with the present embodiment, inspection can be carried outwhile always applying a constant designed contact load on the wafer W,even under the influence of, for example, an increase of a contact loaddue to the increase in the number of devices inspected at one time, anaging of the probe card 22 due to repeated use, and repeated thermalexpansions and contractions of the probe card 22 due to a thermalinfluence, e.g., an accelerated test performed at a high temperature. Asa result, the inspection can be performed with a higher reliability.

In accordance with the present embodiment, there is prepared the contactload monitoring device 10 in which the displacement sensor 11 positionedin the space underneath the support member 21A measures a displacementof the reference surface 21B at the bottom end side of the supportmember 21A as an amount of sinking of the main chuck 21 during anoverdrive stage. The contact load monitoring device 10 always accuratelydetect the amount of sinking of the main chuck 21 during the overdrivestage. Further, the present embodiment includes the control device 23for monitoring the designed contact load based on the measurement resultfrom the displacement sensor 11. The control device enables a constantcontact load (designed contact load), thereby realizing a highlyreliable inspection. Since the control device performs the inspectionunder an optimum contact load, the lifetime of the probe card 22 can beextended. The displacement sensor 11 may be an analog or a digitaloutput displacement sensor of a contact or a non-contact type. Thedisplacement sensor 11 can promptly correct a contact load without adeformation thereof and, in addition, estimate a high precision contactload.

In accordance with the present embodiment, since the displacement sensorfor measuring the amount of sinking of the main chuck is placed in thespace below the main chuck, an efficient use of space is possiblewithout requiring an additional space for the installation of thedisplacement sensor. Further, by not using, for example, a linear scalewhose scale varies depending on a change in temperature, a measurementprecision can be improved.

Furthermore, though a center of the bottom end surface of the supportmember 21A is used as the reference surface at the bottom side of themain chuck 21 in the present embodiment, a plurality of spotssurrounding the center of the bottom end surface of the support member21A can be used as reference surfaces. In such case, a plurality ofdisplacement sensors 11 are respectively installed at positionscorresponding to the plurality of reference surfaces, as illustrated inFIG. 4. The displacement sensors are preferably equidistanced from thecenter. Furthermore, any flat surface other than the one located at thecenter of the main chuck 21 and the bottom end surface of the supportmember 21A can also be used as a reference surface.

Though the above embodiment has been described for the case of using thecontact load monitoring device 10 in the probe device 20 for inspectingthe wafer W, the contact load monitoring device 10 can be widelyemployed for various objects to be inspected, e.g., substrates for LCD.

INDUSTRIAL APPLICABILITY

The present invention provides a probe device capable of performing aninspection with an enhanced inspection reliability by allowing an objectto be inspected to contact probes under a constant contact load whilepromptly and accurately estimating a contact load and correcting it to apredetermined value.

Other features and modifications may be conceived by those skilled inthe art. Therefore, the present invention is not limited to therepresentative embodiments disclosed herein but should be understoodfrom a wider viewpoint.

Accordingly, it is apparent that various changes and modifications maybe made without departing from the interpretation and scope of theinventions broadly defined in the following claims and theirequivalents.

1. A probe device for inspecting electrical characteristics of an objectW to be inspected, comprising: a mounting table for mounting thereon theobject to be inspected, the mounting table being movable in X, Y, Z andθ directions; a probe card disposed above the mounting table andprovided with a plurality of probes; and a contact load monitoringdevice including at least one displacement sensor and a control deviceand monitoring a contact load exerted on the mounting table by theprobes during an overdriving stage, wherein the displacement sensor isdisposed in a space below the mounting table and measures, as an amountof sinking, a displacement of a reference surface at a bottom side ofthe mounting table caused by the contact load exerted on the mountingtable by the probes during the overdriving stage; wherein the controldevice is provided with a correlation table for amounts of sinking ofthe reference surface of the mounting table and contact loads andestimates a contact load by using the displacement measured by thedisplacement sensor and the correlation table; and wherein the controldevice adjusts the contact load to be identical with a designed contactload by further elevating the mounting table in case the contact load isless than the designed contact load.
 2. The probe device of claim 1,wherein the displacement sensor is one of an analog and a digital outputdisplacement sensor.
 3. The probe device of claim 1, wherein thedisplacement sensor is one of a capacitive displacement sensor and aneddy current displacement sensor.
 4. The probe device of claim 1,wherein the displacement sensor is disposed on at least one of a centerof the mounting table and a plural locations therearound.
 5. A methodfor inspecting electrical characteristics of an object to be inspectedby using the probe device of claim 1, comprising the steps of: (a)setting a designed overdriving amount and a designed contact loadcorresponding to the object W to be inspected in the control device; (b)bringing the object to be inspected into contact with the probes byelevating the mounting table on which the object to be inspected ismounted; (c) overdriving the mounting table based on the designedoverdriving amount; (d) monitoring whether the contact load exerted onthe mounting table is identical with the designed contact load by usingthe contact load monitoring device, wherein the monitoring step (d)includes the steps of: (d1) measuring the displacement of the referencesurface at a bottom side of a support member as the amount of sinking ofthe mounting table and outputting the measured displacement to thecontrol device by the displacement sensor disposed in a space below themounting table; (d2) estimating the contact load corresponding to thedisplacement based on the correlation table and comparing the estimatedcontact load with the designed contact load by the control device; (d3)further elevating the main chuck in case the contact load estimatedbased on the displacement measured by the displacement sensor is lessthan the designed contact load; and (d4) repeating the steps (d1)through (d3) and stopping the elevation of the main chuck when thecontact load based on the displacement measured by the displacementsensor reaches the designed contact load; and (e) inspecting theelectrical characteristics of the object W to be inspected.
 6. A probedevice for inspecting electrical characteristics of an object to beinspected, said probe device comprising: a movable mounting tableconfigured to mount thereon the object to be inspected; a probe carddisposed above said movable mounting table and provided with a pluralityof probes; and a contact load monitoring device including a displacementsensor and a control device, said contact load monitoring device beingconfigured to monitor a contact load exerted on said mounting table bysaid plurality of probes during an overdriving stage, wherein saiddisplacement sensor is disposed underneath said mounting table, saiddisplacement sensor being configured to measure a displacement of areference surface at a bottom side of said mounting table during theoverdriving stage, wherein said control device is provided with acorrelation table for estimating the contact load based on thedisplacement of said reference surface, and wherein said control deviceis configured to adjust the contact load to be equal to a designedcontact load by moving said mounting table to achieve a displacement ofsaid reference surface that correlates to the designed contact loadbased on the correlation table.
 7. The probe device of claim 6, whereinsaid displacement sensor is one of an analog displacement sensor and adigital output displacement sensor.
 8. The probe device of claim 6,wherein said displacement sensor is one of a capacitive displacementsensor and an eddy current displacement sensor.
 9. The probe device ofclaim 6, wherein said displacement sensor is disposed on at least one ofa center of said mounting table and plural locations therearound.
 10. Amethod for inspecting electrical characteristics of an object to beinspected using a probe device including a movable mounting table, aprobe card provided with a plurality of probes, and a contact loadmonitoring device including a displacement sensor and a control device,said method comprising the steps of: (a) setting a designed overdrivingamount and a designed contact load corresponding to the object to beinspected in the control device; (b) bringing the object to be inspectedinto contact with the probes by elevating the mounting table on whichthe object to be inspected is mounted; (c) overdriving the mountingtable based on the designed overdriving amount; (d) monitoring whetherthe contact load exerted on the mounting table is identical with thedesigned contact load by using the contact load monitoring device,wherein the monitoring step (d) includes the steps of: (d1) measuring adisplacement of a reference surface at a bottom side of the mountingtable as an amount of sinking and outputting the measured displacementto the control device, using the displacement sensor disposed underneaththe mounting table; (d2) estimating the contact load corresponding tothe displacement based on a correlation table in the control device andcomparing the estimated contact load with the designed contact load;(d3) further elevating the main chuck in case the contact load estimatedbased on the displacement measured by the displacement sensor is lessthan the designed contact load; and (d4) repeating the steps (d1)through (d3) and stopping the elevation of the main chuck when thecontact load based on the displacement measured by the displacementsensor reaches the designed contact load; and (e) inspecting theelectrical characteristics of the object to be inspected.